Hey 

All the universities and colleges offeres their application forms once the board exams are over . Therefore you can expect the dates between may -june for the availability of forms . The forms may be available in online or offline mode or both .

You're gonna take admission in b.com plain for your undergraduation so  ,as you've not mentioned the name of any college and university, so each and every college and university have their own dates of collecting application for admissions. You should visit the websites of the college and university in which you want to take admission.you'll get the above information there.
All the best.

If you are looking for admission to b com then different college/Univ have different dates for admission